[gjs/wip/chergert/avoid-zero-of-str] profiler: avoid clearing 512 bytes of stack

[Christian Hergert <chergert src gnome org>]

commit 925911ee7d59166d83bf16b7813ef88a7df6bde7
Author: Christian Hergert <chergert redhat com>
Date:   Wed Jun 5 18:27:04 2019 -0700

    profiler: avoid clearing 512 bytes of stack
    
    If {0,} is used, the whole array will be zeroed on each iteration of the
    loop. That is not ideal as we could be deep in the stack here.

 gjs/profiler.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/gjs/profiler.cpp b/gjs/profiler.cpp
index 6f37eaca..d7ee03b5 100644
--- a/gjs/profiler.cpp
+++ b/gjs/profiler.cpp
@@ -317,7 +317,7 @@ gjs_profiler_sigprof(int        signum,
          * 512 is an arbitrarily large size, very likely to be enough to
          * hold the final string.
          */
-        char final_string[512] = { 0, };
+        char final_string[512];
         char *position = final_string;
         size_t available_length = sizeof (final_string) - 1;
 
@@ -348,9 +348,12 @@ gjs_profiler_sigprof(int        signum,
             if (dynamic_string_length > 0) {
                 size_t remaining_length = MIN(available_length, dynamic_string_length);
                 memcpy(position, dynamic_string, remaining_length);
+                position += remaining_length;
             }
         }
 
+        *position = 0;
+
         /*
          * GeckoProfiler will put "js::RunScript" on the stack, but it has
          * a stack address of "this", which is not terribly useful since